Impact While Running And Injury

All women, and all heel-strikers (to control those variables):

"Greater vertical impact loading in female runners with medically diagnosed injuries: a prospective investigation"

"Conclusions Vertical average loading rate was lower in female runners classified as ‘never injured’ compared with those who had been injured and sought medical attention."

From the NYT: 

"“One of the runners we studied, a woman who has run multiple marathons and never been hurt, had some of the lowest rates of loading that we’ve ever seen,” said Irene Davis, a Harvard professor who led the study. She pounded far less than many runners who land near the front of their feet, Dr. Davis said. “When you watched her run, it was like seeing an insect running across water. It was beautiful.”"

Yep, makes sense.

"From the book Born to Run, I remember a quote from Caballo Blanco:

“Think Easy, Light, Smooth, and Fast. You start with easy, because if that’s all you get, that’s not so bad. Then work on light. Make it effortless, like you don’t give a shit how high the hill is or how far you’ve got to go. When you’ve practiced that so long that you forget you’re practicing, you work on making it smooooooth. You won’t have to worry about the last one – you get those three, and you’ll be fast.” 

It's the "practiced that so long that you forget you're practicing" part that trips most people up.  If you rush it, in almost any sport, that's when you get hurt.